1. Field
The present invention relates to a load distribution device, a load distribution program, and a load distribution method for receiving processing request(s) from terminal(s) and allocating and transferring the processing request(s) to at least one of a plurality of servers.
2. Description of the Related Art
In recent years, there is a service provider server that provides various services such as Web sites, e-mail, IP (Internet Protocol) phones, and file servers on an IP network. The service provider server provides services using, for example, the Web, FTP (File Transfer Protocol), and Telnet to the clients. As the users increase and the dimensions of the services become large, certain measures need to be taken in the service provider servers to provide stable services. An example of the measures includes increasing the number of service provider servers with performance remaining about the same as the existing service provider servers. In that case, a load distribution system is built up in which a load distribution device is used to distribute the load to a plurality of service provider servers.
The load distribution device is a device that receives requests of processing from terminals of service users (clients) and that allocates the requests to a plurality of service provider servers providing the same services, thereby reducing the load to specific service provider servers. The load distribution device is installed, for example, between the terminals of the clients and a service provider server group. The installation of the load distribution device can prevent degradation of the service quality due to a concentrated load on specific service provider servers and can pursue providing comfortable services to the clients.
Even after the operation of the service provider server is started, updates of software or hardware constituting the service provider servers are needed for various factors such as for correcting bugs, improving functions, and improving the security. Examples of the updates of software of the service provider servers include upgrading applications, applying security patches, and updating kernels and firmware. The maintenance person uses a portable storage medium such as a CD (Compact Disk) and a flash memory to update the software in some cases. An appliance server including an automatic update function updates the software of the service provider server in other cases.
The appliance server is a server designed and developed for specific applications. The appliance server including the automatic update function automatically detects software update information (patches) through a network in collaboration with a provider vendor to deal with the detection of security holes or failures. The appliance server then automatically executes an updating operation of a server to be maintained based on the detected update information.
The operation of the service provider server is unstable during the update of software of the service provider server. Therefore, the service providing function needs to be stopped. For example, a method for changing the software configuration of server is proposed, in which calculation process requests from the clients are not distributed to a server whose software configuration will be changed, and the software configuration is changed after a certain period of time or after the number of calculation process requests remaining in the server is checked (see, for example, Japanese Patent Laid-Open No. 2006-285315).